1. Field of the Invention
The present invention relates to a device for treating biological liquids to remove undesirable substances contained therein, and more specifically to a device for filtering and biospecifically purifying biological liquid such as blood.
2. Description of The Related Art
At present there are many pathologies associated with the presence of undesirable components in the blood. It is, therefore, worthwhile to have the capability to selectively clear the blood of these substances. Many devices have been proposed for this purpose.
French patent application 2,035,134 proposes a device for eliminating proteins or specific amino acids from the blood by passing blood over an active substance. However, such a device carries major drawbacks such as the risk of degrading specific elements of the blood, particularly erythrocytes thus causing hemolysis.
Since the undesirable substances that one wishes to eliminate from the blood are present in the liquid fraction of the blood which is called blood plasma, it has been proposed to treat only the blood plasma. French Patent Application 2,325,390 discloses this type of a first device for separating the plasma from the specific elements of the blood and a second device in series with the first device for purifying the plasma. Although this system has the advantage of not requiring contact between the specific elements of the blood and the treatment agent contained in the purification device, it has the drawback of requiring the circulation of a considerable quantity of liquid plasma. Since this quantity is withdrawn from the patient's blood circulation, it is very important to minimize the amount withdrawn as much as possible.
In European Patent Application E-P 139,949 a device has been proposed comprising an internal bundle of hollow fibers constituting a semipermeable membrane, and intended to separate the plasma from the specific elements of the blood. This bundle of hollow fibers is surrounded by a treatment chamber containing an agent for treating the plasma. The blood, circulating inside the hollow fiber is treated through filtration by the agent. This device uses the processes of filtration and retrofiltration. As the blood to be treated enters the first section of the device, the pressure of the blood inside the fibers causes plasma to pass from the inside of the fibers towards the treatment chamber by convection. Conversely, in the second section, near the outlet of the device, the pressure of the blood inside the fibers is lower than the pressure of the plasma in the treatment chamber, causing the plasma to filter back and rejoin the blood enriched with specific elements. The plasma obtained by filtration of the blood through the wall of the hollow fibers is treated by an agent contained in the treatment chamber. Therefore, a recombination of the specific elements of the blood with the purified plasma is obtained in the second section of the device, and flows through the outlet.
Although this system remedies a certain number of drawbacks of the prior art, it has the disadvantage of being limited by the plasma filtration flow through the semi-permeable membrane. In fact, in order for the processes of filtration and retrofiltration to be used for plasmapheresis, the difference in pressure on either side of the membrane must cancel out at the center of the module, requiring a zero flow of filtration at that point.
To increase overall plasmafiltration flow, it is necessary to either increase the filtration surface, the blood flow, or the drop in pressure of the blood inside the device. In view of its limited filtration capacity, such a device does not make it possible to meet present performance requirements.
U.S. Pat. No. 4,361,484 proposes a blood purification device having a microporous membrane, wherein the pores on a portion of the membrane remote from the passing blood hold a biologically active substance. The patent also discloses a purification device comprising means for subjecting the blood to be purified to pressure variations so as to produce an alternating passing of a fraction of the blood through the micropores of the membrane. Thus, only the plasma fraction of the blood to be purified penetrates through the micropores of the membrane and comes into contact with the biologically active substances.
Such a device eliminates the preliminary stage of plasma filtration and prevents contact between the blood cells and the biologically active substances. However, apart from being complicated to operate, such a device presents serious manufacturing difficulties. Moreover, it seems difficult to attain an adequate purification rate with such a device.
Thus, the biospecific purification devices of the prior art do not allow for satisfactory treatment of a biological liquid such as blood.
An object of the present invention is to provide a biospecific purification device, not having the drawbacks of the prior art and permitting good purification of a biological liquid such as blood without the risk of destroying cells.
Another object of the present invention is to provide a biospecific purification device, not requiring the circulation of a large quantity of liquid.
Another object of the present invention is to provide a biospecific purification device that is easily manufactured at low cost.
Another object of the present invention is to provide a biospecific purification device with good efficiency relative to the size and bulk of the device.
Another object of the present invention is to provide a biospecific purification device which is simple to operate, reliable, and has all the necessary patient safeguards.
The foregoing objects are provided by a device for biospecifically purifying a liquid having a first portion containing cellular elements and a second portion without cellular elements, said device comprising, a casing means for conducting said liquid into said casing, means disposed within said casing for tangentially filtering said first portion from said second portion, means disposed within said casing for transversely filtering said second portion to biospecifically purify the liquid after the separation of said cellular elements, means for evacuating said first portion and said second portion from said casing.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.